UNINTERRUPTIBLE POWER SUPPLY SYSTEM WITH ENGINE START-UP

Abstract

An uninterruptible power supply system has a regulated power source, an electrical generator electrically interconnected to the regulated power source, an engine having a main shaft integral with or coupled to the shaft of the electrical generator, a rotating rectifier mounted onto a shaft of the electrical generator, a mains power supply, a switch connected between the electrical generator, the mains power supply and a synchronous machine of the regulated power source, a synchronous generator, and an uninterruptible load. The regulated power source has a housing, a synchronous machine, a synchronous generator, and a flywheel sharing a common shaft. The electrical generator has a shaft coupled to a combustion engine. The switch transfers power from the synchronous machine to the electrical generator to cause the electrical generator to rotate its shaft or the main shaft of the engine. A short-stop load is supplied power from the electrical generator.

Claims

1. A power supply system comprising: a regulated power source having a housing, a synchronous machine, a synchronous generator, and a flywheel sharing a common shaft in the housing; an electrical generator electrically connected or interconnected to said regulated power source, said electrical generator having a shaft therein; an engine having a main shaft integral with or coupled to said shaft of said electrical generator; a mains power supply; a switch connected between said electrical generator and said mains power supply and the synchronous machine of said regulated power source, said switch adapted to transfer electric power from the synchronous machine of said regulated power source to said electrical generator so as to cause said electrical generator to rotate the shaft thereof in order to rotate the main shaft of said engine during startup of said engine; and a load, the synchronous generator of said regulated power source supplying power to said load and electrically independent of an electric power supplied to the synchronous machine.

2. (canceled)

3. (canceled)

4. (canceled)

5. (canceled)

6. The power supply system of claim 1, the synchronous machine driving the common shaft of said regulated power source, said regulated power source having a power line, the power line being connected to said switch.

7. The power supply system of claim 1, said synchronous machine comprising: an excitation stator winding; an excitation rotor winding cooperative with said excitation stator winding, said excitation rotor winding rotating with a rotation of the common shaft of said regulated power source; a main stator winding; a main rotor winding cooperative with said main stator winding, said main rotor winding affixed to said common shaft and rotatable with the rotation of the common shaft of said regulated power source; and a squirrel cage winding cooperative with said main stator winding and said main rotor winding, said squirrel cage winding being rotatable with the rotation of the common shaft of said regulated power source.

8. The power supply system of claim 7, said regulated power source further comprising: a voltage controller electrically connected to said excitation stator winding of said synchronous machine so as to cause a voltage to develop in said main stator winding.

9. The power supply system of claim 7, further comprising: a rotating rectifier affixed to the common shaft and electrically connected to said excitation rotor winding and said main rotor winding of the synchronous machine of said regulated power source.

10. The power supply system of claim 1, said regulated power source being switchable by said switch so as to be electrically connected to the mains power supply so as to supply power from said mains power supply to said regulated power source.

11. (canceled)

12. (canceled)

13. The power supply system of claim 1, said electrical generator comprising: a main stator winding; a main rotor winding mounted on the shaft of said electrical generator, said main rotor winding cooperative with said main stator winding; a squirrel cage winding cooperative with said main stator winding and said main rotor winding; an excitation stator winding; and an excitation rotor winding cooperative with the shaft of said electrical generator and cooperative with said excitation stator winding.

14. The power supply system of claim 13, said electrical generator further comprising: a rotating rectifier affixed to the shaft and electrically connected to said excitation rotor winding and to said main rotor winding.

15. The power supply system of claim 14, further comprising: an automatic voltage regulator electrically connected to said excitation stator winding.

16. (canceled)

17. (canceled)

18. The power supply system of claim 1, said engine being an internal combustion engine.

19. The power supply system of claim 1, said mains power supply being a three-phase AC power supply.

20. The power supply system of claim 1, said electrical generator acting as an induction motor when said switch causes power to flow from said regulated power source to said electrical generator, the induction motor being cooperative with the main shaft of said engine so as to cause the main shaft of said engine to rotate.

21. (canceled)

22. (canceled)

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0049] FIG. 1 is a diagrammatic illustration of the power supply system of the present invention.

[0050] FIG. 2 is a cross-sectional view showing the electrical generator and engine of the power supply system of the present invention.

[0051] FIG. 3 is a cross-sectional view of the regulated power source of the present invention.

[0052] FIG. 4 is a plan view showing the rotating rectifier is used in the present invention.

[0053] FIG. 5 is electrical schematic of the rotating rectifier is used in the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0054] Referring to FIG. 1, there is shown the power supply system 10 in accordance with the preferred embodiment of the present invention. The power supply system 10 includes a regulated power source 12 having a synchronous machine 13, a synchronous generator 31 and a flywheel 16 with a common shaft 14 in a housing 15. An electrical generator 18 is coupled to an engine 19 and is electrically connected to the regulated power source 12 by a switch 22. The switch 22 is connected between the electrical generator 18, the mains power supply 20 and the regulated power source 12. The switch 22 transfers power from the regulated power source 12 to the electrical generator 18 so as to cause the electrical generator 18 to rotate a shaft of the electrical generator 18 in order to correspondingly rotate the main shaft of the engine 19, during startup of the engine 19 and supplies power from the engine 19 and electrical generator 18 to the regulated power source 12 after engine startup.

[0055] In FIG. 1, the regulated power source 12 includes a synchronous machine 13 that acts as an induction motor, a synchronous motor and a synchronous condenser, or a synchronous generator with the common shaft 14. The synchronous machine 13 can act as a synchronous condenser. The regulated power source 12 has an incoming/outgoing power line 26 connected from the synchronous machine 13 of the regulated power source 12 to the switch 22.

[0056] The synchronous machine 13 of the regulated power source 12 includes an excitation stator winding 28, an excitation rotor winding 30, a main rotor winding 32, a squirrel cage winding 72 (as shown in FIG. 3), and a main stator winding 34. A voltage controller 36 is electrically connected to the excitation stator winding 28 so as to cause a voltage to develop in the main stator winding 34 during startup of the engine 19 so that power flows out of the regulated power source 12 as the flywheel 16 rotates the common shaft 14 or to regulate reactive power generation for power factor correction when the regulated power source 12 is connected to the mains power supply 20. A rotating rectifier 38 (also shown in FIG. 3) is affixed to the common shaft 14 of the regulated power source 12. The rotating rectifier 38 is cooperative with the excitation rotor winding 30, the main rotor winding 32, the voltage controller 36, and the main stator winding 34. The regulated power source 12 can be switchably electrically connected to the electrical generator 18 so as to supply or receive power to or from the electrical generator 18. The switch 22 electrically connects the synchronous machine 13 of the regulated power source 12 to the mains power supply 20 to maintain synchronous speed and act as a synchronous condenser for the mains power supply 20, or electrically connects the synchronous machine 13 of the regulated power source 12 to the electrical generator 18, (which will act as a load during startup of engine 19) when the regulated power source 12 supplies power from the regulated power source 12 to the electrical generator 18. After startup of engine 19, the electrical generator 18 will supply power to the synchronous machine 13 of the regulated power source 12.

[0057] The electrical generator 18 includes a main stator winding 40, a main rotor winding 42, a squirrel cage winding 64 (as shown in FIG. 2), an excitation stator winding 44 and an excitation rotor winding 46. The main rotor winding 42, the squirrel cage winding 64, and the excitation rotor winding 46 are cooperative with the shaft 60 (as shown in FIG. 2) so as to rotate the shaft 60 of the electrical generator 18. A rotating rectifier 48 is mounted on the shaft 60 of the electrical generator 18 and electrically connected to the excitation rotor winding 46 and to the main rotor winding 42. An automatic voltage regulator 50 is electrically connected to the excitation stator winding 44 so as to monitor and control voltage of the main stator winding 40 of the electrical generator 18.

[0058] FIG. 1 shows that the regulated power source 12 includes a synchronous generator 31 whose rotor is mounted to the common shaft 14 and whose stator is mounted on the housing 15 of the regulated power source 12. The flywheel 16 is mounted on the common shaft 14. As such, as the common shaft 14 rotates with the rotation of the flywheel 16, this rotation causes the synchronous generator 31 to produce electric power which can be delivered to the uninterruptible load 55 in a completely independent electrical circuit. Synchronous generator 31 is a complete synchronous generator including independent excitation and voltage regulator 99. As such, uninterruptible load 55 will receive electrical energy from the synchronous generator 31 of the regulated power source 12. This creates an electrical power circuit that is electrically isolated from the mains power line 20, electrical generator 18 and synchronous machine 13 of the regulated power source 12. The configuration of the synchronous generator 31 is similar to the configuration of the electrical generator 18 (described hereinbefore), and is designed specifically to create an isolated grid with robust voltage stability.

[0059] The switch 22 has an incoming power switch 52 and an outgoing power switch 54. There is an interlock that allows for only one of the switches to be closed at any given moment. The incoming power switch 52 is in a closed position so as to supply power from the mains power supply 20 to the regulated power source 12. The incoming power switch 52 is in an open position so as to disconnect the mains power supply 20 from the regulated power source 12 and to allow the outgoing power switch 54 to close. The outgoing power switch 54 is in a closed position so as to supply or receive power between the regulated power source 12 and the electrical generator 18. The outgoing power switch 54 is in an open position so that the electrical generator 18 is disconnected from the regulated power source 12 and allows for the incoming power switch 52 to close.

[0060] The incoming power switch 52 is in a closed position and the outgoing power switch 54 is in an open position so as to supply power from the mains power supply 20 to the regulated power source 12. The incoming power switch 52 is in the open position and the outgoing power switch 54 is in the closed position so that power flows to and from the regulated power source 12 and the electrical generator 18.

[0061] In the present invention, the engine 19 is an internal combustion engine. The mains power supply 20 is a three-phase AC power supply. The electrical generator 18 is a synchronous generator enabled to act as an induction motor when the switch 22 causes power to flow from the regulated power source 12 to the electrical generator 18 during startup of the engine 19. When this electrical generator 18 acts as an induction motor, the induction motor is cooperative with the main shaft of the engine so as to cause the main shaft of the engine to rotate.

[0062] The power supply system 10 works as follows. Initially, the regulated power source 12 is accelerated by the synchronous machine 13 acting as a synchronous motor so as to remain at its full nominal speed (which is also at synchronous speed). This occurs by being connected to the switch 22 to the mains power supply 20. The uninterruptible load 55 receives power from the synchronous generator 31 of the regulated power source.

[0063] When it is connected to the mains power supply 20, the synchronous machine 13 of the regulated power source 12 acts as a synchronous condenser so as to provide KVARs in order to improve power factor. This increases the efficiency of the system and improves voltage stability on the mains power supply 20. The regulated power source 12 also acts to increase frequency stability in the mains power supply 20 because of the inertia of the flywheel.

[0064] When a fault is detected on the mains power supply 20, the power supply system 10 will command the engine 19 to start. Engine 19 startup will commence by opening the incoming power switch 52. Simultaneously, the voltage controller 36 will halt excitation to the synchronous machine 13 of the regulated power source 12. Then, the outgoing power switch 54 will be closed. Because the excitation is off, this will permit for a low transient when closing the outgoing power switch 54. As a result, the power supply system 10 will not experience any electrical or mechanical power conditions that are damaging to the components. After closing the outgoing power switch 54, the synchronous machine 13 of the regulated power source 12 will connect to the electrical generator 18. Voltage controller 36 will now operate to create a voltage in the main stator winding 34 of the synchronous machine 13 of the regulated power source 12.

[0065] Because the synchronous machine 13 of the regulated power source 12 is not connected to any incoming external power source, and because it is spinning, the and because it has excitation from voltage controller 36, the synchronous machine 13 of the regulated power source 12 will now act as a synchronous generator that delivers the accumulated kinetic energy in the flywheel 16 to drive the electrical generator 18 as an induction motor. It will do this by means of the voltage controller 36 so as to deliver power to the excitation stator winding 28. This causes a voltage to be developed in the leads of the main stator winding 34. Therefore, power will flow out from the synchronous machine 13 of the regulated power source 12.

[0066] When this occurs, because the electrical generator 18 is at a stand-still, and because its rotor has a squirrel cage winding 64, and because it can be fed electrical power to the leads of the main stator winding 40, the electrical generator 18 will act as an induction motor. As such, it develops higher torque as voltage originating in the synchronous machine 13 of the regulated power source 12 is increased. During this phase, the leads of the main rotor winding 42 will be connected to each other in short-circuit by way of the rotating rectifier 48 (to be described hereinafter). This allows for even further torque to be developed. This torque will cause the shaft 60 of the electrical generator 18 to turn. As such, the main shaft 62 of the engine 19, which is coupled to the shaft 60 of the electrical generator 18, will also turn. The main shaft 62 of the engine 19 will continue to accelerate as it turns. It will eventually meet the required turning conditions of the main shaft 62 of the engine 19 so as to allow for combustion to occur in the engine 19.

[0067] At this point in time, regulated power source 12 remains engaged and assists in the acceleration of the engine 19 and thus the time to bring the engine 19 to full speed is reduced. The voltage controller 36 will regulate the power required at each stage of the acceleration so as to optimize this operation as well as to protect the components from power conditions that might damage any of the components. As the synchronous machine 13 of the regulated power source 12 remains engaged during acceleration, it will supply power to the electrical generator 18 as long as the synchronous machine 13 has a higher frequency than the electrical generator 18. Once their frequencies are matched, the synchronous machine 13 will return to acting as a synchronous motor and the electrical generator 18 will act as a synchronous generator, and the engine 19 will continue to supply power to reach the synchronous speed and will also provide energy to the synchronous machine 13 of the regulated power source 12 to recover the speed and kinetic energy that was lost during the startup of the engine 19. This can occur if either the voltage controller 36 or the automatic voltage regulator 50 is engaged. This is because of the fact that both the synchronous machine 13 of the regulated power source 12 and the electrical generator 18 have squirrel cage windings. Either can act as an induction motor as long as the other is spinning faster, and with excitation, acting as a synchronous generator. However, the simultaneous operation of both the voltage controller 36 and the automatic voltage regulator 50 is carefully coordinated to prevent damaging transient conditions.

[0068] Any over-speed of the engine 19 cannot occur by the present invention because the regulated power source 12 is spinning at synchronous speed and frequency (which are equal for both the regulated power source 12 and the electrical generator 18). It cannot supply electrical power or torque to the engine 19 if the electrical generator 18 has higher frequency than the synchronous frequency. The regulated power source 12 also adds inertia in case the speed governor of the engine 19 tends to overshoot. This inertia will reduce the acceleration tending to any overspeed. Therefore, the system is protected against over-speed during startup and operation.

[0069] After the engine 19 reaches the nominal synchronous speed of the electrical generator 18, startup of the engine 19 is complete. Electrical generator 18 now supplies power to the synchronous machine 13 of the regulated power source 12. The uninterruptible load 55 receives power from the synchronous generator 31 of the regulated power source 12 before, during and after the mains power supply 20 failure. Power from the synchronous generator 31 is without switching or transients that could negatively affect the quality of such power.

[0070] After startup, the engine 19 and the electrical generator 18 can also deliver power to a short-stop load 50 byway of closing external switch 23 to that short-stop load 50. The engine 19 and the electrical generator 18 will continue to operate normally, supplying the power for both the regulated power source 12 and the short-stop load 50. The synchronous machine 13 of the regulated power source 12 will act as a synchronous condenser with high inertia. This provides reactive power to correct power factor and improve voltage and frequency stability to the short-stop load 50.

[0071] After the mains power supply 20 is reestablished, a monitoring period confirms that the mains power supply 20 is stable. At this point, the synchronous machine 13 of the regulated power source 12 is disengaged by suspending power supplied by the voltage controller 36 and immediately disconnected by opening the outgoing power switch 54. Then, the incoming power switch 52 will be closed and the voltage controller 36 will resume its operations so that the regulated power source 12 resumes operation powered by the mains power supply 20, and remains ready for any subsequent failure of the mains power supply 20 that may later arise. The operation of engine 19 and electrical generator 18 can now be suspended. Short-stop load 50 can be powered off or it can be connected to the mains power supply 20 by means of the external switch 23 (if the external switch 23 is a two-way transfer switch) or other switch (not shown). The synchronous generator 31 continues to supply power to the uninterruptible load 55.

[0072] The rotating rectifier 48 in the electrical generator 18 can be specially designed to function so that the rotating rectifier 48 will connect both ends of the main rotor winding 46 in short-circuit during cranking operations in order to improve the rising torque produced by the electrical generator 18 (acting as an induction motor) during startup of engine 19.

[0073] The method of the present invention is easy to apply since it is applicable to most traditionally commercially available gen-sets. The rotating rectifier 48 will mimic its functionality as in synchronous motors during starting conditions. Although the system of the present invention does not require any traditional method of engine starting, it can be used in addition to any traditional method of engine starting. It can therefore result in a redundant configuration that increases reliability of engine-startup. The electrical generator 18 can also be electromagnetically selected and designed for optimizing the performance of this starting method, by using the previously described rotating rectifier, adding a larger squirrel cage, among other design details that enhance behavior as an induction motor.

[0074] FIG. 2 is a cross-sectional view showing the configuration of the electrical generator 18 and the engine 19. As can be seen, the electrical generator 18 has a shaft 60 positioned therein. Shaft 60 can be coupled to the main shaft 62 of the engine 19. Alternatively, the shaft 60 of the electrical generator 18 can be integral with the main shaft 62 of the engine 19. The squirrel cage winding 64 and the main rotor winding 42 are mounted on the shaft 60 so as to rotate with the rotation of the shaft 60. The electrical generator 18 includes the main stator winding 40, the main rotor winding 42 and the squirrel cage winding 64. The electrical generator 18 also includes the excitation stator winding 44 and the excitation rotor winding 46. A rotating rectifier 48 is affixed to the shaft 60 so as to rotate with the rotation of the shaft 60. Similarly, the excitation rotor winding 46, the mains rotor winding 42 and the squirrel cage winding 64 will also rotate with the rotation of the shaft 60.

[0075] In FIG. 2, it can be seen that the engine 19 is an internal combustion engine. The electrical generator 18 and the engine 19 can be mounted together so that the shafts 60 and 62 thereof can be easily integrated or coupled.

[0076] FIG. 3 shows a cross-sectional view of the regulated power source 12 of the present invention. The regulated power source 12 includes the flywheel 16 and the common shaft 14. The flywheel 16 is mounted to the common shaft 14 that extends upwardly within the housing 15 of the regulated power source 12. All rotating components of the synchronous machine 13 and the synchronous generator 31 are mounted on the common shaft 14. The synchronous machine 13 of the regulated power source 12 has the main stator winding 34, the main rotor winding 32 and the squirrel cage winding 72. The squirrel cage winding 72 is cooperative with the main rotor winding 32, the common shaft 14, and with the main stator winding 34. The main rotor winding 32 and the squirrel cage winding 72 will rotate with the rotation of the common shaft 14. The synchronous machine 13 of the regulated power source 12 further includes the excitation stator winding 28, the excitation rotor winding 30 and rotating rectifier 38. The excitation rotor winding 30, rotating rectifier 38 and the main rotor winding 32 are electrically connected and will rotate with the rotation of the common shaft 14.

[0077] In FIG. 3, it can be seen that the common shaft 14 and the housing 15 extend upwardly so as to accommodate the synchronous generator 31. All rotating components of the synchronous machine 13 and the synchronous generator 31 are mounted on to the common shaft 14. The synchronous generator 31 of the regulated power source 12 has a main stator winding 43, a main rotor winding 45 and the squirrel cage winding 47. The squirrel cage winding 47 is cooperative with the main rotor winding 45, the common shaft 14, and the main stator winding 43. The main rotor winding 45 and the squirrel cage winding 47 will rotate with the rotation of the common shaft 14. The synchronous generator 31 of the regulated power source 12 further includes an excitation stator winding 49, an excitation rotor winding 41 and rotating rectifier 39. The excitation rotor winding 41, the rotating rectifier 39 and the main rotor winding 45 are electrically connected and will rotate with the rotation of the common shaft 14. Squirrel cage winding 47 will also rotate the rotation of the common shaft 14.

[0078] FIG. 4 illustrates the rotating rectifier 48 as used in the electrical generator 18 of the present invention. The rotating rectifier 48 is a bridge rectifier which it is mounted on a rotor. Neither brushes nor slip rings are used. As such, the rotating rectifier 48 serves to reduce the number of wearing parts. The electrical generator 18 (as with most alternators) has a rotating field and a stationary armature (i.e. power generation windings). By means of the voltage regulator 50 varying the amount of current through the stationary exciter stator windings 44, in turn, varies the three-phase output from the excitation rotor winding 46, which is rectified to direct current in the rotating rectifier 48 to feed the main rotor winding 42. This rotating rectifier 48 has the additional function of placing the terminals of the main rotor winding 42 in short-circuit in order to increase the torque of the electrical generator 18 when it acts as an induction motor during startup of the engine 19. The rotating rectifier 48 opens the short-circuit and resumes normal rectifying functions after engine startup.

[0079] The rectifier 48 includes a DC bus 100 and 102 (as shown in FIG. 5), a fast recharge diode 82, resistors 84, anode diodes 86, and cathode diodes 88. These components are mounted on the rectifier rotor 90 which can be a fixed to the shaft 60 of the electrical generator 18. Zener diodes 92 and SCRs 110 are also provided on the rectifier rotor 90 to create a short-circuit between the opposing poles of the DC bus 100 and 102, which correspond to the two leads of the main rotor winding 42.

[0080] FIG. 5 illustrates the electrical schematic associated with the rotating rectifier 48 of the present invention. In the schematic diagram, there is a positive DC bus 100 and a negative DC bus 102. The center of line 104 is one of the exciter rotor winding 46 terminals that are connected in parallel to both the anode diode 86 on the positive DC bus 100 and the cathode diode 88 on the negative DC bus 102. Line 106 and line 108 connect in a similar fashion as line 104. Resistors 84 are placed on the line extending between the positive DC bus 100 and negative DC bus 102. The SCR 110 controls the flow of electricity across the DC bus between the positive DC bus 100 and the negative DC bus 102 in short-circuit during startup of engine 19. This also places the leads of the main rotor winding 42 in short-circuit. SCRs 110 are activated by line 144 which includes the Zener diode 92 along with resistors 112 and 116.

[0081] After the end of the engine startup operation described hereinabove and after the engine 19 reaches the nominal synchronous speed of the electrical generator 18, the regulated power source 12 will remain connected to the electrical generator 18. As such, the electrical generator 18 can work either as an induction generator or as a synchronous generator, depending on which excitation system is designated in order to operate in constant running engine conditions. The synchronous machine 13 of the regulated power source 12 will receive power produced by the engine 19 in order to recover velocity and return to synchronous speed of the regulated power source 12. The synchronous generator 31 of the regulated power source 12 will continue to supply uninterruptible power to the uninterruptible load 55 without the need for any switching to occur on the output ofthe synchronous generator 31.

[0082] In the present invention, the regulated power source 12 includes the synchronous machine 13, the synchronous generator 31, the housing 15, the common shaft 14, and the flywheel 16. The synchronous generator 31 cooperates with the rotating components that cooperate with the common shaft 14 and with the flywheel 16 of the regulated power source 12. The synchronous machine 13 and the synchronous generator 31 each have their own independent voltage regulators, excitation windings and rotating rectifiers. The synchronous generator 31 can supply uninterruptible power to the uninterruptible load 55 without the need for any switching to occur on the output of the synchronous generator 31. The synchronous generator 31 is electrically independent from the rest of the power supply system.

[0083] In normal operating conditions, the uninterruptible load 55 receives power from the synchronous generator 31 of the regulated power supply 12 (whose common shaft 14 is powered by the synchronous machine 13), which, in turn, is powered by the mains power supply 20. If any failure occurs in the mains power supply 20, before engine 19 is started and up to full speed of engine 19, the synchronous generator 31 continues to deliver power to the uninterruptible load 55 because the common shaft 14 continues to rotate because of the inertia in the flywheel 16. When engine startup is achieved through the aforementioned method, the engine 19 delivers power to the synchronous machine 13 of the regulated power source 12, which, in turn, continues to deliver power to in an uninterruptible fashion to the uninterruptible load 55 via the synchronous generator 31 of the regulated power source 12. After the mains power supply 20 is reestablished and deemed safe, the synchronous machine 13 of the regulated power source 12 is disengaged by opening the outgoing power switch 54. Then, the incoming power switch 52 will be closed and the voltage controller 36 will resume its operations so that the regulated power source 12 resumes operation powered by the mains power supply 20, and remains ready for any subsequent failure of the mains power supply 20. Engine 19 and electrical generator 18 can now suspend operation. During all these operations, the regulated power source 12 continues to spin at synchronous or near-synchronous speed and the synchronous generator 31 continues to supply power to the uninterruptible load 55 without harmful switching or fast-acting electrical transients on the supply to the uninterruptible load 55.

[0084] To facilitate commissioning, the rotating rectifier 38 of the synchronous machine 13 has the same functionality as the rotating rectifier 48 of the electrical generator 18. During commissioning the regulated power source 12 must be accelerated from a stand-still. In order to achieve this, the synchronous machine is used as an induction motor thanks to its squirrel cage and the rotating rectifier 38 placing the leads of the main rotor winding 32 in short circuit to increase the torque of the synchronous machine during commissioning. Therefore, FIG. 4 and FIG. 5 also describe the rotating rectifier 38 of the synchronous machine 13 of the regulated power source 12. An additional (not shown) centrifugal switch or radio-controlled switch may be added to the rotating rectifier 38 if a reduced-voltage motor-start method is used.

[0085] The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction can be made within the scope of the appended claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.